The present invention relates to a semiconductor device having a packaged structure, and a method of producing the semiconductor. In particular, the present invention relates to a semiconductor device of a resin sealing type produced with Wafer-level Chip Size Package (WCSP) technology. In the semiconductor device, an antenna is formed on a surface of a semiconductor substrate opposite to a surface with an element formed thereon.
Patent References 1 and 2 have disclosed conventional semiconductor devices, in which an inductor used as an antenna and a semiconductor element are formed on a same substrate. Such a semiconductor device includes a wireless Integrated Circuit (IC) tag having an antenna for reception and transmission.
In the conventional semiconductor device, in which the inductor used as the antenna and the semiconductor element are formed on the same substrate, it is not necessary to provide a substrate for disposing the antenna, thereby making it possible to reduce a size of the semiconductor device. In a semiconductor device, in general, a semiconductor element is formed on one surface of a semiconductor substrate (element forming surface), and an antenna is formed on an interlayer insulation layer or a passivasion layer formed to cover the semiconductor element. That is, the semiconductor element and the antenna are formed on the same surface.
Patent reference 3 has disclosed a configuration, in which a conductive layer connected to earth is disposed between an antenna and a semiconductor element.    Patent Reference 1: Japanese Patent Publication No. 2003-243570    Patent Reference 2: Japanese Patent Publication No. 05-48328    Patent Reference 3: Japanese Patent Publication No. 05-67919
In the conventional semiconductor device described above, the antenna is formed on the element forming surface of the semiconductor substrate. In this case, when a signal is received or transmitted, the semiconductor element receives influence from radio wave emitted from the antenna. Accordingly, characteristic of the semiconductor element may be deteriorated, or the semiconductor device may malfunction.
In order to solve such a problem, the antenna may be formed on a surface of the semiconductor substrate opposite to the element forming surface (refer to Patent References 1 and 2).
According to the technology disclosed in Patent Reference 1, bumps are formed on the element forming surface and the opposite surface for electrically and mechanically connecting the semiconductor device to a mounting substrate. Accordingly, the antenna and the bump are formed on the same surface of the semiconductor substrate. In such a configuration, when the semiconductor device is mounted on the mounting substrate, the antenna is sandwiched between the semiconductor substrate and the mounting substrate. Accordingly, reception sensitivity of the semiconductor device may lower, or intensity of transmitted radio wave may decrease.
According to the technology disclosed in Patent Reference 2, the antenna is formed on a surface of the semiconductor substrate opposite to the element forming surface. However, Patent Reference 2 does not specify which direction the surface with the antenna formed thereon is arranged relative to the mounting substrate when the semiconductor device is mounted on the mounting substrate. Accordingly, it is difficult to solve the problems described above.
In view of the problems described above, an object of the present invention is to provide a semiconductor device capable of reducing influence received by a semiconductor element when an antenna emits radio wave. Another object of the present invention is to provide a method of producing the semiconductor device.
Further objects and advantages of the invention will be apparent from the following description of the invention.